Recently, as technical development and demands for mobile devices have increased, demands for rechargeable secondary batteries as energy sources are rapidly increasing, and thus more researches on the secondary batteries are being carried out to cope with such diverse demands. Also, the secondary batteries have attracted considerable attention as power sources for an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (Plug-In HEV), which have been proposed as solutions for air pollution and the like caused by conventional gasoline and diesel vehicles that use fossil fuels.
Accordingly, the electric vehicle (EV) traveling using only a battery and the hybrid electric vehicle (HEV) using a battery with a conventional engine have been developed and partially have been commercialized. Although a nickel-metal hydride (Ni-HM) secondary battery among the secondary batteries is mainly used as a power source for EV and HEV, in resent years, researches on lithium secondary battery having high energy density, high discharge voltage, and output stability have been actively progressing and partially have been commercialized.
When such secondary batteries are used in devices or apparatuses that require high capacity, e.g., a power source or a power storage system for vehicles, the secondary battery necessarily has a form of a battery cell assembly or a battery module in which a plurality of battery cells are arranged.
In general, such battery cell assembly or battery module has a structure having improved stability by a plurality of outer cover members surrounding outer surfaces thereof so as to prevent deterioration in performance or degradation in stability caused by physical damages on the battery cells constituting the battery cell assembly or the battery module in various operation circumstances of the device or the apparatus.
FIGS. 1 and 2 are schematic exploded views illustrating various structures of a conventional battery module.
Firstly, referring to FIG. 1, a battery module 100 includes a battery cell assembly 110 and an outer cover member surrounding an outer surface of the battery cell assembly 110.
The battery cell assembly 110 has an overall hexahedral shape in which a plurality of battery cells 111 are arranged in a direction of one surface while being electrically connected to each other at electrode terminals 112.
The outer cover members 121 and 122 include a first packing member 121 and a second outer cover member 122.
The first and second outer cover members 121 and 122 are coupled to surround the rest outer surfaces except for first and second surfaces facing each other with reference to a protruding direction of the electrode terminal 112 of the battery cells 111 constituting the battery assembly 110.
The first outer cover member 121 has a plate-type structure bent in a -shape on a vertical cross-section so as to consecutively surround front, top, and bottom surfaces, which are disposed adjacent to each other, among the rest outer surfaces except for the first and second surfaces of the battery cell assembly 110.
The second outer cover member 122 has a single plate-type structure to surround the rest bottom surface except for the front, top, and bottom surfaces surrounded by the first outer cover member 121 among the rest outer surfaces except for the front and rear surfaces of the battery cell assembly 110.
The first and second outer cover members 121 and 122 are coupled through welding in a state in which corners 121a, 121b, 122a, and 122b corresponding to each other contact each other to form a structure surrounding the battery cell assembly 110.
Referring to FIG. 2, a first outer cover member 221 and a second outer cover member 222 forms a plate-type structure bent in a -shape on a vertical cross-section to respectively surround one surface-and-a top surface and the other surface-and-a bottom surface, which are disposed adjacent to each other in a consecutive manner, among the rest outer surfaces except for the first and second surfaces facing each other of the battery assembly 210.
The rest structure except for the above-described structure is the same as that of the battery module in FIG. 1.
However, since the outer cover member is coupled to the battery cell assembly through welding while directly surrounding the outer surface of the battery cell assembly in a state in which an additional cover or a protection member is not disposed between the battery cell assembly and the outer cover member so that the battery module has a maximum capacity in a limited space, the battery cell assembly may be damaged by spark or missiles generated in a welding process.
Also, the damage on the battery cell assembly due to the spark may cause a risk such as explosion of the battery cell assembly and act as a factor making a poor working circumstance for a worker during working.
Furthermore, in the welding process of the outer cover member, a welded portion for minimizing such a limitation may not be easily determined. In this case, since time required for the welding to couple the outer cover members to each other increases, the time and costs required for manufacturing the battery module may also increase.
Thus, techniques for fundamentally solving the above-described limitations are highly demanded.